Methods of forming hemisperical grained silicon on a template on a semiconductor work object

ABSTRACT

The present invention provides a method of preparing a surface of a silicon wafer for formation of HSG structures. The method contemplates providing a wafer having at least one HSG template comprising polysilicon formed in BPSG, the HSG template being covered by silicon dioxide. The wafer is treated with a cleaning agent to clean the surface of the wafer. Next, the wafer is treated with a conditioning agent. The conditioning agent removes native oxide from the HSG template without excessively etching structural BPSG. Preferably, the conditioning agent also removes a thin layer of polysilicon on the HSG template. The wafer is then transferred to a process chamber for HSG formation.

This invention claims the benefit of co-pending U.S. application Ser.No. 10/361,107, entitled “Method Of Forming Hemispherical GrainedSilicon On A Template On A Semiconductor Work Object”, filed Feb. 7,2003 which is a continuation of U.S. application Ser. No. 09/303,385,entitled Method Of Forming Hemispherical Grained Silicon On A TemplateOn A Semiconductor Work Object”, filed May 1, 1999, the entiredisclosures of which are hereby incorporated by reference as if setforth in their entireties for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to a method of cleaning and conditioning asemiconductor work object, such as a silicon wafer, so that subsequentprocess steps produce desired results. More particularly, the presentinvention provides a method of cleaning and etching a wafer so thatdeposition of amorphous silicon (“a-Si”) on the wafer produces goodformations of Hemispherical Grained Silicon (“HSG”).

HSG formations enhance the storage capacitance in storage devices suchas Dynamic Random Access Memory Arrays (“DRAMS”). Methods for formingHSG are described, for example, in U.S. Pat. Nos. 5,634,974 and5,759,262, which are hereby incorporated by reference as if set forth intheir entirety. More particularly, these patents describe a method ofseeding and annealing a-Si on a polysilicon template on a wafer to formHSG. The polysilicon template may be formed in a layer of oxide materialsuch as BPSG. When HSG is formed on the polysilicon template, it becomesthe bottom plate of a capacitor device on the wafer.

During wafer transfer steps, a native oxide layer can form on thepolysilicon template. As described in the aforementioned patents, theformation of a native oxide on a wafer's surface during wafer transfersteps causes significant problems in forming HSG structures on a wafer.This is because HSG formation is very sensitive to surface conditions.If the oxide layer is not removed or inadequately removed, it can impedethe seeding step of the seeding/annealing process in HSG formation.

A persisting problem in HSG formation process is that existing processsteps do not adequately etch the undesired oxide materials from thewafer. Poor, irregularly shaped HSG formations result if the HSG processis not conducted on clean, properly prepped wafers. There are furtherproblems as well.

Existing techniques do not adequately passivate the wafer surface afteretching. Passivation inhibits the reformation of native oxide. Anotheretch-related problem is that conventional etching techniques do not haveacceptable selectivity ratios for the different materials present duringHSG formation. This means either under-etching or over-etching oftargeted materials on the wafer or over-etching of untargeted materialson the wafer. Conventional cleaning and etching techniques may alsoleave the wafer's surface in poor condition for HSG seeding andannealing steps. A brief overview of the cleaning and etching techniquesused on wafers will help illustrate these problems in more detail.

Wafer cleaning steps are usually carried out before etching. Cleaningand etching techniques are well known in the art. The formulation anduse of wafer cleaning solutions and various etchants for silicondioxide, silicon, and other materials such, as silicon nitride aredescribed, for example, in P. Van Zant, Microchip Fabrication: APractical Guide To Semiconductor Processing (3^(rd) ed. 1997)McGraw-Hill, New York, pp. 174-189 & pp. 259-283, which is herebyincorporated by reference. Sulfuric acid based solutions are commonlyused to remove particulate and inorganic contaminants from the surfaceof a wafer. Generally, sulfuric acid based solutions are used at atemperature of about 90° C.-130° C. Oxidants may be added to thesolution so that organic residues are removed from the wafer surface.Suitable oxidants include hydrogen peroxide, ammonium persulfate, nitricacid, and ozone.

Wet etching is commonly used to remove oxide and other materials from awafer: wafers are immersed in an etchant tank for a predetermined time,then rinsed, and dried. Etchants that remove a top layer of materialwithout substantially attacking an underlying layer are said to havehigh selectivity. The selectivity of an etchant is expressed as theratio of the etch rate of one layer of material to the etch rate ofanother layer of material. Typically, selectivity ratios for silicondioxide/silicon are about 20-40, depending on the etch method used.

Silicon oxide is the most commonly etched material on a wafer. Hydrogenfluoride (HF) is an attractive etchant because it dissolves silicondioxide without removing substrate silicon. (As discussed below, thisselectivity is contrary to good HSG formation.) However, at roomtemperature, at high concentrations, HF etches oxide too fast (about 300Å/second). Therefore, HF is typically mixed with water and/or anammonium fluoride (NH₄F) buffering agent. When NH₄F is in the solution,the solution is called a “buffered oxide etch” or “BOE” for short. Itmay be formulated at different strengths for different etch rates. BOEsmay also include a wetting agent to reduce the surface tension of theetchant. One example BOE is an aqueous solution of HF and NH₄F (1:8) atroom temperature. The etch rate is about 700 Å/min. A more aggressiveetchant for silicon dioxide is acetic acid and NH₄F (2:1) at roomtemperature, which has an etch rate of about 1000 Å/min. Differentetchants may be used to etch other material deposited on a wafer. Forexample, aqueous mixtures of nitric acid (HNO₃) and HF have been used toetch polysilicon deposited on a wafer.

At least the following etchants have been used to remove the oxide layerfrom an HSG template prior to introducing the wafer into the seeding andannealing steps: (1) 100:1 wt. % HF solution; (2) HF vapor; and (3)unheated HF/TMAH solution. Unfortunately, these etchants suffer from theproblems mentioned above: they may not etch polysilicon, or theyunder-etch or over-etch features on the wafer, or they do not conditiona wafer well for seeding and annealing of HSG. For example, 100:1 HF andunheated HF/TMAH solutions are generally effective at etching a nativeoxide layer to expose the polysilicon template. However, these solutionsdo not etch the underlying polysilicon layer to any appreciable degree,at least not without over-etching oxide layers or rendering thepolysilicon surface in an unsuitable condition for HSG formation. Stillother etchants are problematic to use. For example, HF vapor etchantsare not only highly aggressive (especially on BPSG) and difficult tocontrol, but they also require more complicated application andcontainment equipment than required for etchant in solutions. HF vaporsystems may also pose hazards to workers.

Another disadvantage of conventional etchants and methods is that theymay not passivate the surface of the wafer adequately. Passivationinhibits the reformation of native oxide on the wafer that could occurduring staging between process steps. This means shortened staging timesbetween processing steps. Longer staging times are desirable toaccommodate the lag between the cleaning and etching steps and the HSGformation steps.

For the foregoing reasons, there is a significant need for improvedmethods for cleaning and etching methods. The etchants used in suchmethods must etch selectivity ratios that are not too high or low andmust leave the wafer in good condition for HSG formation. They shouldalso passivate the wafer surface to inhibit reformation of oxidematerial during staging times.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art bydoing one or more of the following:

-   -   Cleaning the surface of a wafer without disrupting the integrity        of HSG template.    -   Etching native oxide from an HSG template without over-etching        other structures on the wafer.    -   Conditioning the HSG template for HSG formation by removing a        thin layer of the HSG template.    -   Passivating the surface of the wafer to inhibit reformation of        native oxide and increase staging time for the wafer.

One embodiment of the present invention is directed to a method ofpreparing a surface of a semiconductor work object for formation of HSGstructures, comprising: providing a work object having at least one HSGtemplate; treating the work object with a cleaning agent to clean thesurface of the wafer; treating the cleaned work object with aconditioning agent to condition the template for HSG formation; anddirectly transferring the conditioned work object to HSG seeding andannealing process steps without a rinse step following treatment withthe conditioning agent.

Another embodiment of the present invention is directed to a method offorming HSG structures on a silicon wafer, comprising: providing a waferhaving at least one HSG template comprising polysilicon; treating thewafer with a cleaning agent to clean the surface of the wafer; treatingthe cleaned wafer with a conditioning agent to condition the templatefor HSG formation; directly transferring the conditioned wafer to HSGseeding and annealing process steps.

Another embodiment of the present invention is directed to a method ofpreparing a surface of a wafer for formation of HSG structures,comprising: providing a wafer having at least one HSG templatecomprising polysilicon formed in BPSG on a silicon wafer, the HSGtemplate being covered by silicon oxide; treating the wafer with acleaning agent to clean the surface of the wafer; treating the cleanedwafer with a QE2 conditioning agent to condition the template for HSGformation until the silicon oxide layer and at least about 5 Å ofpolysilicon on the HSG template have been removed; and directlytransferring the conditioned work object to HSG annealing and seedingprocess steps.

Another embodiment of the present invention is directed to a method ofpreparing a surface of a wafer for formation of H$G structures,comprising: providing a wafer having at least one HSG templatecomprising polysilicon formed in BPSG on the wafer; treating the waferwith a cleaning agent comprising a solution of sulfuric acid and anoxidant to clean the surface of the wafer; treating the cleaned waferwith a conditioning agent comprising ammonium fluoride and phosphoricacid to condition the template for HSG formation; and directlytransferring the conditioned work object to HSG seeding and annealingprocess steps.

Another embodiment of the present invention is directed to a method offorming HSG structures on wafer, comprising: providing a wafer having atleast one HSG template comprising polysilicon; treating the cleanedwafer with a conditioning agent to condition the template for HSGformation, the conditioning agent removing a predetermined amount ofpolysilicon from the HSG template; and transferring the conditionedwafer to HSG seeding and annealing process steps.

Another embodiment of the present invention is directed to a method offorming HSG structures on a wafer, comprising: providing a wafer havingat least one HSG template comprising polysilicon; treating the cleanedwafer with a conditioning agent to condition the template for HSGformation, the conditioning agent having a pH of about 4.0-7.5 and anetch selectivity ratio for BPSG to silicon dioxide of about 1 to about2, the conditioning agent removing at least 5 Å of polysilicon from theHSG template; and transferring the conditioned wafer to HSG seeding andannealing process steps.

The cleaning agent used in the various embodiments of the presentinvention may be a conventional wafer cleaning solution, such as H₂SO₄with either H₂O₂ or O₃.

The conditioning agent used in the various embodiments of the presentinvention may be an aqueous solution capable of etching oxide andpolysilicon to a predetermined degree. Preferably, such solution has apH of about 4.0 to about 7.5. Preferably, the conditioning agentincludes a fluorine component. The fluorine component may be provided byammonium fluoride or hydrogen fluoride, among other things. Preferably,ammonium fluoride is used in a solution with and a strong acid, thesolution having a pH of about 4.0 to about 7.5. The strong acid may beselected from the group of phosphoric acid, hydrogen fluoride, andhydrochloric acid. The conditioning agent may also comprise an HF/TMAHsolution heated above about 30° C. Preferably the HF/TMAH conditioningagent is heated between about 30° C. to about 45° C. More preferably, itis heated to about 36° C. The conditioning agent may also comprise asolution of nitric acid (HNO₃) and HF or HCl.

Preferably the conditioning agents used in the present invention have anetch selectivity ratio for BPSG to silicon dioxide that is about 1 toabout 2. A preferred conditioning agent sold under the brand name QE2has an etch selectivity ratio of about 1.5 to about 1.6.

Preferably, the conditioning agents of the embodiments of the presentinvention remove at least about 5 Å polysilicon to condition the waferfor good HSG formation. Good HSG formation should also result if atleast 10 Å of polysilicon is removed. Good HSG formation should alsoresult if at least 20 Å of polysilicon is removed. Generally, good HSGformation should also result from removal of about 5 Å or 10 Å to about20 Å of polysilicon.

A work object treated according to the embodiments of the presentinvention may have a staging time of at least about one-hour betweentreatment with a conditioning agent and transfer to HSG seeding andannealing steps.

Preferably, in the embodiments of the present invention, the wafer isdirectly transferred, without rinsing, from the conditioning agent stepto the HSG seeding and annealing process steps.

The HSG templates used in the embodiments of the present may take anyshape. A preferred shape capacitors used in DRAM storage devicescomprises a substantially container shaped structure for forming thebottom plate of the capacitor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of steps defining one or more aspects of thepresent invention.

FIG. 2 is a cross-sectional illustration of a bottom plate being formedin a wafer for a container type capacitor structure prior to cleaningusing the principles of this invention.

FIG. 3 shows the wafer of FIG. 2 after treatment to remove materialsurrounding the container structure, the exposed container now having anative oxide layer that is to be removed according to steps in thepresent invention.

FIG. 4 is the wafer of FIG. 3 after treatment according to certain stepsof the present invention.

FIG. 5 shows the wafer of FIG. 4 after seeding and annealing steps toform HSG.

FIG. 6 shows the wafer of FIG. 5 after a dielectric layer has beenapplied over the HSG formation.

FIG. 7 shows the wafer of FIG. 6 after a layer of top plate material hasapplied over the dielectric layer, completing the capacitor structure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel method for treating asemiconductor work object so that it is suitable for use in HSG processsteps. As used herein, “work object” means wafers (production, dummy, orpmon), die and packaged parts, incorporating, in whole or part, siliconsubstrates, and other known or discovered semiconductor materials,components, and assemblies, including, for example, silicon-on-insulator(SOI), silicon-on-sapphire (SOS), thin film transistor (TFT) materials,or germanium, periodic group III-IV materials, II-VI materials,hetero-materials (II, III, V, VI), and conductive glasses.

It will be apparent to persons of skill in the art that the presentinvention is not necessarily limited to any particular kind of workobject. However, to illustrate the principles of the present invention,the following discussion, unless otherwise noted, will be in terms of asilicon-based wafer as the work object.

FIG. 1 is a flow chart of steps 10-16 that define one or more aspects ofthe present invention. Steps 10-14 relate to pre-treating a wafer sothat it is ready for HSG formation in step 16. Generally, step 16includes the steps of seeding and annealing to form HSG. Preferably, anRTCVD process chamber is used in the process of forming HSG.

As a matter of convenience, steps 10-14, unless otherwise noted, may beperformed at about 1 ATM and at about room temperature, or they may beperformed at other ambient conditions in a fabrication facility. Thesesteps may be carried out on a semi-automated wet bench. Step 16 may becarried out in any process chamber suitable for formation of HSG,including PECVD, LPCVD, RTCVD, and PVD process chambers, as noted inU.S. Pat. No. 5,759,262, previously incorporated by reference.

FIG. 2 is a cross-sectional illustration of a container-type capacitorstructure 18 being formed on a silicon substrate 20. The container 18represents the bottom plate (electrode) of the capacitor onto which HSGwill be formed to enhance the capacitor's storage capacity. It will beapparent to persons skilled in the art that although the Figures depictonly a single capacitor, this invention applies to the formation of aplurality of capacitors on a single wafer. It will also be apparent,that while this invention is generally in terms of a container-typecapacitor structure, the principles will readily apply to other patternson work-objects intended to receive HSG formations. Hereinafter, apatterned region on a wafer intended to receive HSG formations isreferred to as an “HSG template”.

An HSG template may be formed by well-known techniques. Referring toFIG. 2, a conductive material is deposited over a selectively etchedlayer 22 of dielectric material to form container 18. Container 18 isformed of the conductive material. Preferably, the conductive layer ofmaterial forming container 18 is polysilicon. FIG. 2 shows the container18 after removal of the wafer's top layer of conductive material fromthe wafer's top surface, by for example, chemical-mechanical polishing(CMP). After polishing down the top surface of the conductive material,container 18 material remains in the well formed in dielectric layer 22,as illustrated in FIG. 2.

The dielectric layer 22 may be an un-doped or doped silicon dioxidematerial deposited on silicon wafer 20. A preferred dielectric materialfor layer 22 is BPSG (borophosphorus silicate glass). BPSG is a dopedsilicon dioxide oxide. Other possible dielectric materials includeun-doped and doped silicon nitride material. The dielectric layer 22 isused structurally to support the HSG templates and to separate HSGcapacitor cells to keep the cells from electrically shorting each other.For purposes of illustrating this invention, the dielectric layer 22 isgenerally described herein in terms of BPSG. It should be recognized,however, that other dielectric materials may also be suitable for use indielectric layer 22.

FIG. 3 shows the wafer of FIG. 2 after treatment to etch dielectriclayer 22. This treatment may be based on known etching methods. Asuitable method for etching BPSG involves a wet etch using an aqueoussolution of about 100:1 wt % HF. The etch exposes the walls of containerstructure 18, as shown in FIG. 3. After etching to remove the oxidematerial 22, a native oxide layer 24 may form on container 18.

Prior to introducing the wafer into HSG fabrication steps, the surfaceof the wafer must be cleaned of organic and other contaminants. Theoxide material 24 must also be removed from the HSG template 18.Preferably, the surface of the wafer is also passivated to inhibitreformation of oxide on the. wafer's surface during staging betweenprocess steps.

If such surfaces are not adequately cleaned and conditioned, HSG mayform poorly on the HSG template. If the formations are too poor, thedevice may be defective, lowering production yields.

To avoid such problems and produce good formations, the presentinvention uses a novel method of cleaning and conditioning a wafer priorto HSG formation. To illustrate the principles of the present invention,the wafer of FIG. 3 may be treated according to steps 10-14 of FIG. 1.After these steps, the wafer may be introduced into step 16, HSGformation.

In step 10, a wafer surface with an HSG template is cleaned by acleaning agent to remove organics or other contaminants from the wafer'ssurface. Wafer cleaning agents are well known. For example, sulfuricacid based solutions are commonly used to remove particulate andinorganic contaminants from the surface of a wafer surface. Generally,sulfuric acid based solutions are used at a temperature of about 90°C.-130° C. Oxidants may be added to the solution so that the solutionalso removes organic residues. Suitable oxidants include hydrogenperoxide, ammonium persulfate, nitric acid, and ozone. As previouslynoted above, the formulation and use of these cleaning solutions is wellknown to persons skilled in the art.

In selecting a suitable cleaning agent, the cleaning agent should not beso strong that it substantially disrupts the integrity of the HSGtemplate. A preferred cleaning agent is, for example, a “Piranha”solution. Piranha cleaning agents are well known in the art. Typically,the Piranha solution comprises aqueous H₂SO₄ with either H₂O₂ or O₃.Piranha is carried out at about 120° C. at 1 ATM for about 5 minutes oruntil the wafer surface and HSG template have been acted on to a desireddegree. This cleaning step removes inorganic and organic contaminatesfrom the wafer's surface.

In step 12, the HSG template is etched with a conditioning agent toremove layer 24 of native silicon dioxide and preferably to remove athin layer of polysilicon layer 18. The conditioning agent exposes andconditions the surface of the HSG template so that good HSG seeding andannealing result in subsequent steps. Removal of at least about 5 Å ofthe top layer of polysilicon from the HSG template is believed to resultin good HSG formation. Generally, removal of at least about 5-20 Å ofpolysilicon should produce good results. The etch should be conductedwithout excessive etching of the remaining BPSG layer 22. Excessiveetching of layer 22 may lead to poor integrity of the capacitorstructures. A suitable etch ratio of BPSG to silicon dioxide is about1.0 to about 2.0 so that there is not unacceptable loss of the BPSGlayer. A preferable ratio is about 1.0.

This invention contemplates using different conditioning agents toremove native oxide and a thin layer of polysilicon without unacceptableetching of BPSG or other material. For example, the present inventioncontemplates using as a conditioning agent a solution of ammoniumfluoride (NH₄F) with phosphoric acid (H₃PO₄,), hydrogen fluoride (HF),hydrochloric acid (HCL), or another strong acid. Another conditioningagent contemplated by the present invention is a solution of HF or HCLwith nitric acid (HNO₃). Generally, the conditioning agent should beformulated for a pH range of about 4.0-7.5. Preferably, the pH isadjusted to about 7.0.

A preferred conditioning agent for use in the present invention is aknown solution sold under the brand name “QE2” by OLIN Corporation,Norwalk, Conn. QE2 is an aqueous solution containing about 40 wt. %NH₄F, about 1.0-1.3 wt. % phosphoric acid (H₃PO₄,), and deionized wateras the remainder. A QE2 etchant can etch BPSG at about 75 Å/min andsilicon dioxide at about 48 Å/min. This gives a BPSG/oxide etchselectivity ratio of about 1.6. This ratio is considered a suitableratio for the purposes of this invention. A QE2 conditioning agentetches the polysilicon stated above at about 20 Å/min.

Conveniently, the QE2 conditioning agent may be used without heating atabout room temperature at about 1 ATM. However, the present invention isnot limited to this temperature. The temperature may be in the range ofabout 15° C. to about 60° C. The process is carried out for about 1-5minutes or until the oxide layers or other targeted layers have beenetched to a desired degree. Temperatures at the lower end of thetemperature range will require longer times. Times and temperatures maybe adjusted to control how much polysilicon or other substrate materialis etched. It is believed that the foregoing conditions of useapplicable to a QE2 conditioning agent should also generally apply forthe use of the other conditioning agents contemplated by the presentinvention. In any event, persons skilled in the art will recognize howto adjust such conditioning agents' formulation and how to use them toproduce desired results.

A conditioning agent having a passivation agent is advantageous becausethe component transfers to the surface of the wafer to passivate it. Thepassivation agent keeps the surface from oxidizing, allowing arelatively long staging time before the wafer experiences significantoxidation. Fluorine and hydrogen from a QE2 conditioning agent arebelieved to transfer to the surface of the wafer to passivate it. It isexpected that other conditioning agents with a fluorine component willproduce similar results. A QE2 conditioning agent used according to thepresent invention should allow a staging time of at least about fourhours between use of the conditioning agent and the HSG seeding andannealing process steps.

Another conditioning agent of the present invention is a heated aqueoussolution of HF/TMAH (tetramethyl ammonium hydroxide). A preferredsolution comprises about 0.5 wt. % HF and about 1.5 wt. % TMAH. Thissolution has a BPSG/thermal oxide etch selectivity of about 2:1. Aconditioning agent based on HF/TTMAH should be heated to at least about30° C. when applied to the HSG template. Preferably, the conditioningagent is applied at a temperature of from about 30° C. to about 45° C.Preferably the temperature is about 36° C. Above 45° C., the solutionmay cause pitting in the polysilicon. It has been found that HF/TMAHsolutions below about 30° C. do not etch effectively enough to result ingood selective HSG formation. One reason may be that such solutions etchlittle or no polysilicon after etching the native oxide layer and/orthey do not leave the surface of the wafer in a state conducive to HSGseeding and annealing.

After treatment with a conditioning agent, the wafer may be driedwithout rinsing. It is undesirable to rinse the wafer because commonaqueous rinsing agents could promote the reformation of native oxide onthe wafer, which would interfere with HSG formation. The wafer may bedried by transfer to a dryer. A suitable drying technique is at aboutroom temperature in a Marangoni dryer. Other systems for drying wafersare well known in the art. After drying, the wafer surface is favorablyconditioned for HSG formation. After the wafer is dried, the wafer maybe transferred to an RTCVD system or other system suitable for producingHSG formations on the wafer. The transfer of the wafer directly to HSGformation process steps, without rinsing or further chemical processing,following use of the conditioning agent is hereinafter referred to as a“direct transfer” step.

FIG. 4 shows the wafer of FIG. 3 after steps 10-14 have been performed.At this stage, the native oxide has been removed, the wafer has beendried, and the surface passivated by a passivation agent, such asfluorine from the conditioning agent. The wafer is ready for HSGformation. Methods of forming HSG are described in U.S. Pat. Nos.5,634,974 and 5,759,262, which were incorporated by reference above.

FIG. 5 shows the wafer of FIG. 4 after seeding and annealing steps toform HSG 24 on the HSG template. FIG. 6 shows the wafer of FIG. 5 aftera dielectric layer 26 has been applied over the HSG formation 24. FIG. 7shows the wafer of FIG. 6 after a layer 28 of top plate (electrode)material has been applied over the dielectric layer 26. Layer 28completes the capacitor structure.

Tests were conducted on silicon wafers with container-type polysiliconHSG templates formed in a layer of BPSG. The wafers were treated inaccordance with the foregoing description using a Piranha cleaningagent; a QE2 conditioning agent at about room temperature or an HF/TMAHconditioning agent heated above 30° C.; and direct transfer withoutrinsing. The wafers were then introduced into seeding and annealingsteps for HSG formations. The resulting HSG formations were consistentlybetter than treatment with an etchant solution based on 100:1 HF orunheated (room temperature) HF/TMAH. It is has also been found that goodHSG formations result if HF vapor is used as the conditioning agent.

Persons skilled in the art will recognize the foregoing description andembodiments are not limitations but examples. It will be recognized bypersons skilled in the art that many modifications and variations to thepresent invention are possible that are still within the spirit andscope of the teachings and claims contained herein.

1. A method of forming a semiconductor wafer, comprising: providing awork object with a surface having a polysilicon feature; treating thesurface with a cleaning agent comprising a solution of sulfuric acid andan oxidant to clean the surface; and treating the surface, before HSGformation, with a conditioning agent comprising ammonium fluoride andphosphoric acid to condition the surface for HSG formation by removing athin layer of the polysilicon feature.
 2. A method of forming asemiconductor wafer with the formation of HSG structures, comprising:providing a work object with a surface having a layer of polysiliconmaterial thereon; treating the surface with a cleaning agent to cleanthe surface; and treating the surface, before HSG formation, with aconditioning agent comprising an aqueous solution having a pH of about4.0 to about 7.5 to condition the surface for HSG formation by removinga thin layer of the polysilicon material from the work object.
 3. Themethod of claim 2 wherein the conditioning agent includes a fluorinecomponent.
 4. The method of claim 3 wherein the fluorine component isprovided by ammonium fluoride.
 5. The method of claim 3 wherein thefluorine component is provided by hydrogen fluoride.
 6. The method ofclaim 2 wherein the conditioning agent comprises a solution of ammoniumfluoride and a strong acid, the solution having a pH of about 4.0 toabout 7.5.
 7. The method of claim 6 wherein the strong acid is selectedfrom the group consisting of phosphoric acid, hydrogen fluoride, andhydrochloric acid.
 8. The method of claim 7 wherein phosphoric acid isthe strong acid.
 9. The method of claim 2 wherein the conditioning agentcomprises an aqueous solution containing about 40 wt. % ammoniumfluoride, about 1.0-1.3 wt. % phosphoric acid, and deionized water. 10.The method of claim 2 wherein the conditioning agent comprises anHF/TMAH solution heated above about 30° C.
 11. The method of claim 10wherein the conditioning agent is heated between about 30° C. to about45° C.
 12. The method of claim 11 wherein the conditioning agent isheated to about 36° C.
 13. The method of claim 2 wherein theconditioning agent comprises a solution of nitric acid (HNO₃) and HF orHCl.
 14. The method of claim 2 wherein the cleaning agent comprises asolution of H₂SO₄ with either H₂O₂ or O₃.
 15. The method of claim 7wherein the cleaning agent comprises H₂SO₄ with either H₂O₂ or O₃. 16.The methode of claim 2 wherein the conditioning agent's etch selectivityratio for BPSG to silicon dioxide is about 1 to about
 2. 17. The methodof claim 16 wherein the etch selectivity ratio is about 1.6.
 18. Themethod of claim 2 wherein the work object is directly transferred to theprocess chamber for HSG formation after a staging time of at least aboutone hour.
 19. A method of forming a semiconductor wafer with theformation of HSG structures, comprising: providing a work object havinga surface with plural polysilicon features; treating the surface with acleaning agent to clean the surface; and treating the cleaned workobject, before HSG formation, with a conditioning agent including afluorine component to condition the surface for HSG formation byremoving a thin layer from the polysilicon features.
 20. The method ofclaim 19 wherein the conditioning agent comprises an aqueous solutionhaving a pH of about 4.0 to about 7.5.
 21. The method of claim 20wherein the fluorine component is provided by ammonium fluoride.
 22. Themethod of claim 20 wherein the fluorine component is provided byhydrogen fluoride.
 23. The method of claim 19 wherein the conditioningagent comprises a solution of ammonium fluoride and a strong acid, thesolution having a pH of about 4.0 to about 7.5.
 24. The method of claim23 wherein the strong acid is selected from the group consisting ofphosphoric acid, hydrogen fluoride, and hydrochloric acid.
 25. Themethod of claim 24 wherein phosphoric acid is the strong acid.
 26. Themethod of claim 19 wherein the conditioning agent comprises an aqueoussolution containing about 40 wt. % ammonium fluoride, about 1.0-1.3 wt.% phosphoric acid, and deionized water.
 27. The method of claim 19wherein the conditioning agent comprises an HF/TMAH solution heatedabove about 30° C.
 28. The method of claim 27 wherein the conditioningagent is heated between about 30° C. to about 45° C.
 29. The method ofclaim 27 wherein the conditioning agent is heated between about 36° C.30. The method of claim 19 wherein the conditioning agent comprises asolution of nitric acid (HNO₃) and HF or HCl.
 31. The method of claim 19wherein the cleaning agent comprises a solution of H₂SO₄ with eitherH₂O₂ or O₂.
 32. The method of claim 24 wherein the cleaning agentcomprises H₂SO₄ with either H₂O₂ or O₃.
 33. The method of claim 19wherein the conditioning agent's etch selectivity ratio for BPSG tosilicon dioxide is about 1 to about
 2. 34. The method of claim 33wherein the etch selectivity ratio is about 1.6.
 35. The method of claim19 wherein the work object is directly transferred to the processchamber for HSG formation after a staging time of at least about onehour.
 36. A method of preparing a surface of a semiconductor wafer forformation of HSG structures, comprising: providing a work object havinga surface with a polysilicon feature; treating the surface with acleaning agent to clean the surface; and treating the surface, beforeHSG formation, with a conditioning agent to etch the work object byremoving a thin layer of the polysilicon feature from the work object sothat the polysilicon feature maintains its integrity for HSG formationbut does not over-etch selected portions of the surface of the workobject.
 37. The method of claim 36 wherein the conditioning agentcomprises an aqueous solution having a pH of about 4.0 to about 7.5. 38.The method of claim 36 wherein the conditioning agent includes afluorine component.
 39. The method of claim 38 wherein the fluorinecomponent is provided by ammonium fluoride.
 40. The method of claim 38wherein the fluorine component is provided by hydrogen fluoride.
 41. Themethod of claim 36 wherein the conditioning agent comprises a solutionof ammonium fluoride and a strong acid, the solution having a pH ofabout 4.0 to about 7.5.
 42. The method of claim 41 wherein the strongacid is selected from the group consisting of phosphoric acid, hydrogenfluoride, and hydrochloric acid.
 43. The method of claim 42 whereinphosphoric acid is the strong acid.
 44. The method of claim 36 whereinthe conditioning agent comprises an aqueous solution containing about 40wt. % ammonium fluoride, about 1.0-1.3 wt. % phosphoric acid, anddeionized water.
 45. The method of claim 36 wherein the conditioningagent comprises an HF/TMAH solution heated above about 30° C.
 46. Themethod of claim 45 wherein the conditioning agent is heated betweenabout 30° to about 45° C.
 47. The method of claim 46 wherein theconditioning agent is heated to about 36° C.
 48. The method of claim 36wherein the conditioning agent comprises a solution of nitric acid(HNO₃) and HF or HCl.
 49. The method of claim 36 wherein the cleaningagent comprises a solution of either H₂SO₄ with either H₂O₂ or O₃. 50.The method of claim 42 wherein the cleaning agent comprises H₂SO₄ witheither H₂O₂ or O₃.
 51. The method of claim 42 wherein the conditioningagent's etch selectivity ratio for BPSG to silicon dioxide is about 1 toabout
 2. 52. The method of claim 51 wherein the etch selectivity ratiois about 1.6.
 53. The method of claim 36 wherein the work object isdirectly transferred to the process chamber for HSG formation after astaging time of at least about one hour.
 54. A method of preparing asurface of a semiconductor wafer for formation of HSG structures,comprising: providing a work object having a surface that forms at leastone structure in the form of a polysilicon container-type capacitorhaving sidewalls; treating the surface with a cleaning agent to cleanthe surface; and treating the surface, before HSG formation, with aconditioning agent to condition the surface for HSG formation byremoving a thin layer of the polysilicon container-type capacitor. 55.The method of claim 54 wherein the conditioning agent acts on thesidewalls so that the sidewalls are capable of supporting HSG formation.56. The method of claim 54 wherein the conditioning agent comprises anaqueous solution having a pH of about 4.0 to about 7.5.
 57. The methodof claim 54 wherein the conditioning agent includes a fluorinecomponent.